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Evolution After Darwin: Oparin, Fisher, Wright, Dobzhansky, Mayr, Miller, and Gould.

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Alexander Ivanovich Oparin (1894-1980)

Oparin was a Soviet biochemist, an expert on plants, who became famous for being the author of a 70-page booklet called The Origin of Life, written in 1924. He wondered whether it was possible that molecules made out of carbon, hydrogen, oxygen and nitrogen could have arisen before the existence of life and caused the appearance of the very first cells. Three decades later, Oparin’s ideas bore fruit when Stanley Miller, then a graduate student at the University of Chicago, demonstrated with a series of experiments, that it was possible to synthesize amino acids from inorganic precursors.

Since Oparin had been the first to suggest a plausible solution to the origin of life, he became a Soviet hero. He joined the prestigious Academy of Sciences of the USSR, received numerous awards and medals and all of his books have been translated into many languages. He even received treatment as Head of State in the Soviet Union.

Ronald Fisher, Sewall Wright, Theodosius Dobzhansky y Ernst Mayr

The variation that Darwin saw in his pigeons and barnacles, whose origin, he had not the faintest idea how to explain, emerge as the DNA sequences are changing. Before 1920, the mechanisms that allow evolution to act were unknown. Genes, DNA, and mutations were unknown. There were no explanations as to why there are differences between two populations of the same species. In the early 1920’s, scientists began to realize that mutations had a great impact on evolution. Ronald Fisher (1890-1962), an English statistician, and Sewall Wright (1889-1988), an American geneticist, integrated natural selection and genetics, positioning Darwin’s theory on more solid foundations. Fisher contributed demonstrating that natural selection progresses by the accumulation of small changes, as opposed to the idea of sudden dramatic variations. A significant step was the publication in 1937 of the book by Theodosius Dobzhansky (1900-1975), a Soviet scientist who emigrated to the US, titled Genetics and the Origin of Species. Working with his naked eye and using a microscope, Dobzhansky was able to identify differences in chromosomes by studying diverse populations of fruit flies (Drosophila).

Ernst Mayr (1904-2005) was inspired by Dobzhansky´s book and understood why the traits of the birds he studied in New Guinea, varied from town to town: there was gene flow. By 1940, the architects of the new modern synthesis had shown that genetics, zoology, and paleontology, all told the same story. Mutations were the foundation of evolutionary change. Those mutations, together with the laws of heredity, gene flow, natural selection and geographic isolation, could create new species and new forms of life. If all these changes worked for millions of years, it was possible that the transformations seen in the fossil record would appear. The success of the modern synthesis, also known as Neo-Darwinism, has been the force that has transformed research in evolutionary biology since 1950.

Stanley L. Miller (1930-2007).

As a graduate student at the University of Chicago, Miller became famous in 1951 by showing that what Oparin claimed, could be achieved in practice: it was possible to produce amino acids from molecules containing carbon, hydrogen, oxygen and nitrogen, simulating the conditions of a young, lifeless, primitive Earth. Miller designed a very simple device, consisting of a tube through which a mixture of methane, ammonia, hydrogen and water circulated continuously. When he exposed the gasses to an electric discharge, he found that this process induced the chemical reactions.

The resulting culture was cooled and condensed as rain in the simulated ocean. The experiment ran for a week, and when Miller sampled the water, he found that the result was the formation of seven different amino acids. In just three and a half months, he had proved that Oparin was right. Though he had not been able to create life in the laboratory, the essential and functional constituents of life, the raw material that forms life, had been produced. Still, after 60 years of research, it has not been possible to generate life from scratch in a laboratory.

Stephen Jay Gould (1941-2002)

Gould was one of the most influential evolutionary biologists and paleontologists during the second half of the 20th century. His greatest contribution, postulated together with his colleague Niles Eldredge, was the idea of punctuated equilibrium. They proposed that species appeared in the fossil record, became stable, and then could be subject to rapid events of branching speciation, as opposed to the idea that evolution occurs gradually. This idea arose as an explanation for the scarcity of the fossil record. Gould and Eldredge argued that the fossil record reflects very extended periods of time, during which organisms appear to undergo no changes (a state called stasis), interrupted by sudden leaps (in geological terms) where morphological changes occur. According to them, the lack of fossils is a feature of evolution and not an effect of the lack of data.

The following is one of Gould’s most famous quotes: “Homo sapiens is a tiny twig, born just yesterday on an enormously arborescent tree of life that would never produce the same set of branches if regrown from seed”.  Gould refers to those arrogant humans,  who believe the world was created for us by a god thinking about us.

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